1. Introduction

Fixed partial dentures (bridges) made on implants can be
predictable as long as the diagnosis and treatment planning is done carefully
and some critical success factors are taken into account. The diagnosis and
treatment planning follows the same procedures outlined in Chapter 7 for Single
Tooth Implants and Single Tooth Implant Crowns. Please refer to that section on
pages 51-54 in the Manual.

2. Proper Planning

Anatomical changes necessitate variations from a
conventional fixed partial denture design. The restoring dentist must
anticipate the final design of the prosthesis via diagnostic procedures,
namely:

Articulated diagnostic casts.

Diagnostic wax-up and try-in of teeth.

Surgical stent to diagnostically locate ideal implant
placement.

3. Understanding Anatomical Changes

Resorptive patterns of edentulous spaces may require
surgical replacement of hard and soft tissues for restoration of form and
function. This WILL impact the design of the prosthesis. Due
to the loss of alveolar bone, the resultant fixed partial denture may be
unconventional in design and appearance. The hybrid prosthesis developed by Dr.
George Zarb of the University of Toronto is an example. [Figure 1(a) and
(b)]

Figure 1(a): Hybrid prosthesis – after Dr.
Zarb

Figure 1(b): Hybrid prosthesis – after Dr.
Zarb

The size of the space must be evaluated. Sometimes, it is
best to place 3 bicuspids rather than 2 bicuspids and a molar because the space
is slightly smaller. (Figure 2)

It is also best to have the greatest number of implants
possible. The 3 bicuspids on 3 implants makes for better stress distribution
than 2 bicuspids and a molar on 3 implants (Remember from Chapter 7: Each molar
tooth should really have 2 implants or a wide platform implant). The space size
should be analyzed; the most number of implants that can fit should be planned.

Wide platform, wide implants should also be considered
in the selection.

Another consideration for fixed bridges on implants is the
resulting angulation of the implant and the “draw” of the bridge.
Implants must be placed where the bone is; sometimes that results in them not
being parallel to each other. Special abutments (such as angulated or custom
abutments) can be positioned to allow parallelism of the abutments to each
other. There are abutment selection kits (Figure 3) to facilitate
selecting the right combination of abutments in the laboratory for complex
cases.

Often, making the final impression right down to
the top of the implant fixture (fixture impression) is helpful here. Then the
abutment selection can occur easily in the laboratory. The proper (parallel)
abutments can then be placed in the mouth and a final impression (abutment
impression) can be taken for bridge fabrication.

Figure 3: Abutment Selection Kit

In the maxilla, bone resorbs palatally. Often in the
maxillary posterior, the implants will end up being placed palatally and a
fixed partial denture in crossbite will result. It is important that this is
pointed out to the patient in the diagnostic phase of the treatment plan
(before implants are placed). (Figure 4)

Figure 4: Crossbite in the posterior
maxilla

In the posterior mandible, the direction of the mandibular
nerve rises up, approaching the ridge crest. This often prevents the placement
of enough implants to replace all the teeth that the patient lost. The fact
that the patient will have less posterior teeth after implant
placement should be pointed out to them in advance of treatment. (Figure
5)

Figure 5: Posterior mandible – less
implants means less teeth.

When a large edentulous span has been present for a long
period of time, vertical resorption takes place. The diagnostic wax try-in
should be done to show the patient the longer than usual length of the crowns
or the need for bone grafts to make a more normal size implant crown. Sometimes
pink porcelain can be placed to make up for some of this missing vertical
tissue, but the patient should make this decision in advance before implants
are placed. (Figure 6)

4. Esthetics as a Consideration

Often, esthetics is a specific consideration. In these
cases, the planning must include hard and soft tissue considerations. Soft
tissue considerations include gingival contours and color. Abutment selection
must be made to allow for natural subgingival contours. This could be
accomplished by the EsthetiCone abutment, MirusCone abutment or the fabrication
of a custom abutment.

5. Implant/Natural Dentition

Implants should not be splinted to
natural teeth.

Natural teeth exhibit mobility due to the periodontal
ligament. Implants do not have a periodontal ligament and do
not exhibit mobility. An implant that clinically exhibits
mobility is a failing implant.

There are circumstances where it is necessary to
incorporate natural teeth within an implant assisted fixed partial denture.
These situations provide technical difficulties, uncertain longevity, and no
long-term clinical data to support the concept. In addition, recent data
indicates that the natural teeth under implant supported FPD will actually
intrude.

6. Realistic Expectations

A variety of factors including alveolar ridge resorption
secondary to tooth loss may result in modified fixed partial denture designs,
such as the hybrid prosthesis or a crossbite. It is important that the patient
understands the restorative limitations of the circumstances. Unrealized
expectation may result in realistic litigation.

An implant may have to be placed in
between and not at the planned crown position. This
is because the surgeon must use available bone or avoid anatomic structures.
The resulting implant bridge may be harder to clean and may not exactly match
in esthetics the natural teeth on the patient’s “other side.”

7.1. Stage I (See Chapter 6 in Manual)

Of note is that much vertical and bucco-lingual
resorption can occur and grafting, both bony and soft tissue, is needed for
some multiple tooth implant placements. On occasion the surgeon may need to
correct buccal or occlusal bony defects, discrepancies in papilla height or
differences in cervical height of the adjacent teeth (may also be corrected by
removing tissue from the cervical area of adjacent
short teeth) if an anterior fixed implant
prosthesis is intended. Careful presurgical planning, wax try-ins
without flanges and surgical stents are the keys to success in
implant fixed partial dentures. The more procedures needed to prepare the site,
the more chances of complications.

7.2. Stage II (See Chapter 6 in Manual)

This healing abutment should be 1-2 mm above the soft
tissue. The patient should be instructed to clean this abutment thoroughly so
that the surrounding tissue will heal.

8. Outline of Procedures for Implant Fixed Partial Dentures
(FPD)

Abutment selection

Abutment connection/Interim Prostheses (Temporization)

Final impression

Fabrication of master casts

Wax-up of implant framework

Metal framework try-in

Initial delivery

Check up and post insertion care

8.1. Abutment Selection

Overview (summary) of
Abutments

The prosthesis is usually fastened to the abutment by
a gold prosthetic screw. The abutments for implant fixed partial dentures are
available from the manufacturer in four forms: the standard abutment, the
EsthetiCone, the MirusCone and the angulated abutment. Alternatively, a custom
abutment could be fabricated by a dental laboratory (This is an abutment, which
when screwed into the implant, looks like a crown preparation)

8.1.1. Standard abutment

This abutment is for general use for connecting
multiple implants when esthetics is not a prime consideration.
They are available with a transmucosal height from 3 mm to 10 mm. (Figure
8) The abutment should extend approximately 2 mm above the crest of soft
tissue. This is most often used in the mandible for a hybrid prosthesis
[Figure 1(a) and (b)] where esthetics is not a factor and the
“high water line” design allow easy cleansing.

Figure 8: Standard Abutment

8.1.2. EsthetiCone

For fabricating multiple connected implant bridges
with good esthetics with subgingival margins. The abutments are available with
heights from 1 mm to 3 mm (Figure 9). This abutment has a taper of
15 degrees. The implant fixtures can diverge by 30º without inhibiting the
“draw” of the FPD (see multiunit abutment #6).

8.1.3. MirusCone

The Mirus Cone also allows fabrication of an
esthetic restoration with subgingival margins on multiple connected implants.
It is like an EsthetiCone, only it is smaller in height and is used where
minimum clearance for implant components is available (closed vertical
dimension of occlusion or in the posterior). With its gold cylinder, it is only
4.5 mm. It has a taper of 20º allowing for divergence of approximately 40º for
prosthesis “draw” (Figure 9, see multiunit abutment
#6).

Figure 9: EsthetiCone and MirusCone
Abutments

8.1.4. Angulated Abutment

Anatomical Con-siderations (bone) may result in the
placement of fixtures that might be considered malpositioned (that is, not
parallel to each other). The angulated abutment is employed to correct the path
of insertion of the prosthesis (Figure 10).

The angulated abutment comes in 17° and 30°. It can
correct the angle, but has a wide metal collar which may be
unesthetic. An alternative then would be to use a custom abutment (See #5
below) which can correct the misangulation, and the collar can
be designed (or waxed) with minimum height for esthetics.

Figure 10: Angulated Abutment

8.1.5. Custom Abutment

5. When the implants could not be placed parallel to
each other, esthetics may not allow the use of an angulated abutment as the
angulated abutment results in a wide metal collar which may show if one implant
was not placed far enough subgingivally. In this case, a custom abutment can be
made (Figure 11).

This is a prefabricated cylindrical plastic
component with or without a gold collar. This type of abutment allows direct
wax up over the abutment and is able to be cast into a metal abutment. The
original purpose of this abutment was to create the emergence profile for an
implant placed in an esthetic area. However, when multiple implants are placed
in an unfavorable position, using multiunit abutments may not be able to solve
the problems of both the path of insertion and the esthetics. Using either a
custom abutment (Auradapt) or a prefabricated all titanium adjustable abutment
(TiAdapt) is advocated to achieve a path of draw and esthetics.

Note: a clear thermoplastic
template or silicone Buccal index fabricated from a diagnostic wax up is needed
to guide the wax-up stage of the custom abutment (Auradapt) or titanium
adjustable abutment (TiAdapt).

8.1.6. Multi-Unit Abutment

Developed more recently (2000) for fabricating
multiple connected implant FPD’s (bridges) with good esthetics and
subgingival margins. The heights available are 1, 2, 3, 4, 5, 7, and 9mm. This
has replaced the use of the EsthetiCone and MirusCone. The advantage of a
multiunit abutment versus EsthetiCone or MirusCone is a non-hex abutment
version, which allows easy fitting of the abutment to the implant.

8.1.7. Factors for abutment selection

Use angulated or custom abutment where 15 degrees or
more angle correction is needed.

Distance from the top of the fixture to the crest of the
peri-implant tissue and location of implant (anterior or posterior, upper or
lower)

The height of the abutment shoulder area should be
about 2-3 mm shorter than the crest of the peri-implant tissue in the anterior.
Posterior case selection is variable and depends on esthetics, function, and
cleansability.

8.2. Abutment Connection/Interim Prosthesis

When healing has occurred for 4–6 weeks (the
longer time is for anterior areas), it is time to select the “permanent
or definitive” abutment. This abutment is what the implant crown will be
fabricated on. The abutment is like the crown preparation of a
tooth in the case of a conventional crown.

The operator has the choice of selecting the abutment
intraorally or in the laboratory (Table 1). First, an interim
(transitional) prosthesis must be considered.

Table 1: Abutment Selections -
Options

Do intraorally – remove healing
abutment and measure in mouth with periodontal
probe.

Do in laboratory – first make fixture
impression, pour soft tissue cast. Measure on cast with
periodontal probe.

Place abutment and make abutment
impression.

Place abutment and make abutment impression
or fabricate FPD on fixture cast.

Saves time, cost and one
impression.

More time, cost and possibly additional
impression.

8.2.1. Transitional or Interim Prostheses/Abutment
Selection

The operator has several options to choose from for
stabilizing, protecting and allowing esthetics (in other words an Interim
Prosthesis) for the area surrounding newly exposed multiple
implants. There are 3 options to consider:

Interim Removable
Prosthesis:One option is to leave the healing abutments in
place, relieve and tissue condition the transitional removable
prosthesis (Figure 12). The advantage of this is there is no
temporary fixed bridge fabricated so that the additional cost is minimal (only
cost of tissue conditioning, when necessary.) The disadvantage of leaving the
healing abutments in place, however, is that, at each visit,
the operator will have to remove the healing abutments, place the definitive
abutments and take an x-ray to verify seating while accomplishing the necessary
steps for making the FPD [impression and try-in(s)]. Then the definitive
abutments are removed and the healing abutments are replaced at the end of
each visit.

Alternatively, the dentist can place the
definitive abutment after 4-6 weeks of healing and choose one of these
options:

Interim or Temporary FPD (Bridge)
Fabrication: Make the interim FPD on the definitive abutments. This
interim FPD is removed and replaced at each visit. There is no need to disturb
the definitive abutments. This is an additional procedure, so that the patient
will incur an additional cost.

or

Place Healing Caps: Place Healing
Caps (different from healing abutment. The abutment fits on
the implant; the cap fits on the definitive abutment) over the
definitive abutments, and adjust them so they fit under the
patient’s removable prosthesis. (Should not incur additional cost). The
definitive abutments stay in place. At each visit the caps are removed and
replaced (easy).

Intraoral Selection of the definitive FPD
abutments:

The dentist removes the healing abutments placed by
the surgeon and then follows these procedures:

Armamentarium:

Mirror.

Explorer.

Periodontal probe.

Cotton pliers.

Implant screwdriver for removing healing abutment (large
flat screwdriver shape or gold hexagon shape). Floss is placed on this
screwdriver so it can be retrieved if dropped.

Abutment carrier.

Torque control with drivers.

Gauze.

Technique:

A 2x2 or 4x4 gauze or amalgam squeeze cloth is placed on
the tongue to cover the throat entrance to prevent swallowing or inhalation of
small implant components.

Each healing abutment is removed by turning it counter
clockwise. One is done at a time.

The implant fixture site is irrigated. The top of the
implant fixture should be clean and clear of any bone or soft tissue covering.
If this is not the case, replace the healing abutment and return the patient to
the surgeon for removal of this tissue.

A periodontal probe is used to measure the distance from
the top of the implant fixture to the crest of the peri-implant soft tissue.
The goal is to make sure that the implant FPD margin will be subgingival. It is
best to measure the depth at all six areas (mesiobuccal, midbuccal,
distobuccal; mesiolingual, midlingual, distolingual) so that all areas are
considered, especially the buccal. Record this in the patient record. This must
be done quickly and the healing abutment replaced so as not to have collapse of
the soft tissue cuff leading down to the implant surface (Figure
13).

Figure 13: Measuring the tissue depth for
abutment selection

An EsthetiCone or MirusCone (normal or wide platform)
abutment is selected which is 2-3 mm less than the smallest measurement so that
the crown margin will be below the gingiva in esthetic areas.
The abutment is delivered with its abutment screw as follows:

The abutment is placed by carrying it to the mouth using
an abutment carrier. This carrier is used to place the abutment on the implant
fixture. The carrier is rotated until the operator feels the abutment click
down or seat on the hexagon on top of the implant. The abutment screw is placed
and tightened by hand pressure only (Figure 14). A radiograph is
taken to assure that the abutment is seated. [If the abutment is not available
and needs to be ordered, the healing abutment is replaced and the abutment is
seated at a follow-up visit.]

Figure 14: Carrying and inserting the
EsthetiCone abutment

Once seating is verified by radiograph, the machine
torque control system is used to tighten the abutment completely. The counter
torque device for the EsthetiCone or MirusCone abutment is placed on top of the
abutment in the mouth. The machine screwdriver, hexagonal fit (for EsthetiCone
or MirusCone abutment screw) is placed in the Torque Controller, the torque
controller setting is set at 20 Ncm (45 Ncm for WP) and the abutment is
tightened intraorally until the torque control beeps. Alternatively, a hand
held torque controller may be used (clicks instead of beeping) (Figure
15)

8.2.2. Interim Prosthesis with Definitive
Abutment

EsthetiCone or MirusCone Temporary Caps are placed on
the abutments (Figure 16).

Figure 16: EsthetiCone temporary caps on
abutments

These are manufactured with precise fits and
have room internally for temporary cement. These white polyester resin Caps are
adjusted for occlusion. There should be no interference. Then the appropriate
shade white acrylic resin is placed in the prepared vacuum pressed shell and
placed in the mouth over the temporary caps. This shell with its resin is
removed before the resin sets, while still soft enough to spring out of
undercuts, but firm enough to draw out the temporary caps from the implant
abutments (Figure 17).

Figure 17: Interim (Temporary FPD)

The resulting interim FPD is trimmed for esthetics and
occlusion as usual. It is cemented with a temporary cement.

They can be modified with scissors or scalpel to fit
under the transitional removable prosthesis or the prosthesis is adjusted. It
does not need cement. The cost of this Cap is minimal and so the patient does
not have an additional charge. A summary of Interim FPD choices is shown in
Table 2.

Table 2: Summary of Interim
Prosthesis Choices:

After Stage II surgery, the dentist
can, as a “temporary” prosthesis:

1. Leave healing abutment in place. The
patient continues to wear their removable prosthesis, but the definitive
abutment has to be placed and removed at each visit.

or

2. Select and place the definitive abutment
and use Temporary Caps over the definitive abutments to make
and cement a temporary Implant FPD.

or

3. Select and place the definitive abutment
and use a Healing Cap over the abutment. The patient continues
to wear their removable prosthesis over this.

8.3. Final Impression Procedures

8.3.1. Preliminary Impressions

Preliminary impressions are made to fabricate a
custom tray for the final impression. Preliminary casts can also be used to
gain valuable information for the final design of the prosthesis. These
impressions can be initiated prior to complete healing, usually a few weeks
after healing abutment placement (Stage II surgery). This depends upon the
patients comfort level and soft tissue healing progress.

8.3.2. Technique

Use a stock tray with alginate to obtain an impression,
which captures the implant healing abutments and important anatomical features
such as the retromolar pads and/or maxillary tuberosities to act as guides in
the proper extension of the custom tray (Figure 19).

In a more complex case or one where you suspect that the
alignment of the implants may complicate the design of the prosthesis,
impression copings may first be screwed into the implants before the alginate
impression is made. This will more accurately illustrate the inclination of the
implants (Figure 19).

Use dental stone and carefully pour the impression. If
impression copings were used, replicas must be placed before the impression is
poured. Avoid air entrapment in the implant sites. Allow the stone to set
completely before separating, especially if impression copings are
used.

8.3.3. Custom Tray Fabrication

A custom impression tray is fabricated to increase
the efficiency and accuracy of the final impression. The prosthetic framework
will be constructed on the cast poured from this impression.

Review the basics of custom tray fabrication in your
crown and bridge manual.

Block out: use enough base plate wax to block out
sufficiently around the implants (healing abutments) to allow an unimpeded path
of insertion for the tray and adequate room for impression material around the
implant impression copings and remaining teeth if any.

Custom tray: There are two basic designs for implant
custom trays: the open-top design and the closed top design. The type of tray
made depends upon the type of impression copings used. (See
below).

The closed top tray design is constructed on the
appropriately blocked out cast in the same manner as any custom final
impression tray for a fixed partial denture, treating the implants as teeth.
Build up wax above the healing abutments to allow room for the
tapered impression copings [Figure 20(a)].
Tapered impression copings only can be used with a closed top
tray.

Figure 20(a): Closed-top tray
design

The open-top design is similar to the closed type
except that the surface of the tray above the implant transfers is left open so
that the screws holding the square impression copings in place may be loosened
before the impression is removed [Figure 20(b)].
Square impression copings necessitate an open
top tray.

Figure 20(b): Open-top tray
design

Be sure to cover all important soft and hard
tissue landmarks with your tray.

8.3.4. Final Impression Technique

The final impression is used to fabricate a cast,
which is used to fabricate the final implant prosthesis. The accuracy of this
cast is of paramount importance. The success or failure of the final prosthesis
may well be determined at this stage.

Armamentarium

Impression making components

Impression copings – square or tapered

Guide pins, various lengths, for square impression
copings

Abutment replicas

Screw and hexagonal drivers (screw drivers)

Additional Materials

Impression tray (custom or stock)

Impression material (Impregum)

Impression tray adhesive

Resin, brush, dappen dishes (2)

Dental floss

Slow speed handpiece

Acrylic trimming carbide burs

Impression syringe

The Impression can be made directly to implant
fixtures or implant abutments.

Implant or Fixture Level
Impression

The final impression procedure for both methods is
about the same. However, a fixture level final impression can be selected when
the clinical abutment selection is difficult, a custom abutment is necessary,
or preparation of the abutment is required. Either a disposable stock or custom
tray can be used to obtain a final impression. Both trays have to cover all
hard and soft tissue areas.

This fixture impression will allow the clinician to
select an abutment on a cast in the laboratory. This will be
predictable and will not require the patient to be present. Measuring the
height of the tissue in the mouth and then selecting the correct abutment
chairside cannot always be achieved. Having a cast poured from the fixture
impression will allow the clinician ample time to select,
choose and order the proper abutments in advance to be used at
the next patient visit.

The following is a step-by-step protocol for the
fixture impression technique:

Remove the healing abutment and debride the area.

Place a fixture impression coping and screw it into the
fixture (Figure 21).

Figure 21: Fixture impression coping on
fixture

Take a bitewing/periapical radiograph to verify coping
seating for each implant.

Use Impregum in a tray to make an implant impression.
Square impression copings: A sheet of wax can be placed over the open top to
contain the impression material. Make sure to expose the top of the guide pin
of the impression coping before the watered sets!

Square impression copings: Remove the wax sheet and
unscrew the fixture impression copings, remove the impression and then
immediately replace the healing abutments. Tapered copings: Remove the
impressions as usual.

Make a jaw registration record to use to mount the new
cast poured from this fixture impression.

Trim the cured Polyvinyl siloxane soft tissue mask
material so it will be easily removed from the master cast (no undercut). Use
scalpel blade. See an instructor for this step.

Pour the rest of the impression with a low expansion
(Type IV) stone such as glass ionomer cement.

Separate the cast when it is set. Measure and select the
appropriate abutment as described under Abutment Selection, this chapter.

Order the abutment well in advance of
the next patient visit. (Payment is necessary for this.)

Abutment Level Impression

The abutments were selected and placed in the mouth.
Abutment check: This is a critical step. Using the appropriate driver, check
the tightness of each abutment against the implant fixture. Incomplete seating
at this stage may cause a failure and necessitate a remake of the prosthesis.

Types of abutment impression copings. As discussed
above, there are two basic types of implant impression copings. The two-piece
or square type is designed to be retained in the impression material when the
impression is removed. This type is connected to the abutment by a long guide
pin. This guide pin is disengaged from the abutment before the impression is
removed. An open top tray must be used.

The second type of abutment impression coping (one
piece or tapered) is connected to the implant abutment by an internal screw
which is actually a part of the coping. These impression
copings are designed so that when the impression is removed they stay connected
to the abutment in the mouth. They are then removed separately and replaced in
the impression.

In general the two piece impression or
square impression coping design has less potential for inaccuracy as it is
never removed from the impression. It has the
disadvantage of being longer
occlusogingivally than the one-piece or tapered type and is
more difficult to use where space is a problem (posterior regions)
(Figure 23).

Figure 23: Square impression vs. Tapered
impression coping

Two piece or square impression copings

Seat abutment impression coping. Add an acrylic
resin ring around the square-end coping. Confine the resin to the depressed
middle area of the coping. If a fixture impression was used, this can be done
in the laboratory to save time prior to the actual appointment.

Try in custom tray and adjust extensions as
needed.

Tighten each impression coping with the
appropriate driver.

Place an open top impression tray over the
impression copings and confirm that there is sufficient room around the
impression copings and that the guide pins will be accessible through the open
top of the tray so that they may be unscrewed later. Remove tray and set aside
for later use.

Square impression copings: Join each of the
resin collars with a small amount of resin. Long gaps between copings may be
bridged with the aid of a dental floss bridge and/or wax supports. Add
additional resin after the first application has set. A strong resin joint will
help insure impression accuracy (Figure 24).

Figure 24: Acrylic resin bridge

One-piece impression copings.

Try in custom tray and adjust extensions as needed.

Connect one piece tapered impression copings to the
abutments and tighten with the appropriate driver.

Try in custom tray and confirm that there is
adequate room for the transfer copings has been made and that the tray fits
comfortably.

Impression

Coat the impression tray with polyether impression
material tray adhesive and set aside.

Use the Pentamix machine to mix the material and fill
the syringe and tray.

Carefully inject the Impregum impression material around
and in between the impression copings. Also inject it under the resin bridge if
using the two piece or square impression coping technique.

Carry the loaded impression tray to place over the
impression copings and seat. If an open top tray is being used with the two
piece or square impressions copings press a finger over the open portion of the
tray until the top of all the screws are felt. This will allow visualization of
them when screws need to be loosened to remove the impression (Figure
25). A piece of wax can be placed over the open top tray to contain the
impression material. Make sure the tops of the square impression copings are
visible through the wax.

Figure 25: Square impression coping screw
tops visible in impression

Allow the impression material to set completely.

Remove the set impression as follows:

If you used square impression copings:

Identify the guide pin tops of the two-piece or
square impression copings.

If necessary, clear the tops of the screws by
carefully cutting away excess impression material with a sharp bard sharp
blade.

Unscrew, but do not remove the guide pins. A
“click” will be heard and felt as the guide pin disengages the
fixture. (Figure 26).

Figure 26: Unscrewing the square
impression copings before removing the impression from the mouth

Release the impression and remove from the
mouth.

Examine the impression for detail and
acceptability.

If you used one piece or tapered impression copings:

Remove the tray as usual.

Fabrication of master casts

Attachment of abutment replicas:

Using the appropriate abutment replicas, place one on
each impression coping in the impression and secure lightly by hand or with the
corresponding screw.

Take care not to allow the impression coping to twist in
the impression material.

Soft tissue material (Gi-Mask) is applied around
only the top third of the replica. After setting, die stone will be poured for
the fabrication of the rest of the master cast. After the master cast has set,
it is carefully separated.

8.3.5. Confirmation Jig

Before taking the time and effort to fabricate the
prosthesis, it is wise to confirm the accuracy of the master
cast. This is an extra step and patient visit, but it can save having to cut
and solder the FPD framework.

On the master cast, remove any and all impression
copings and their resin bridge if any.

Replace all square impression copings
back on the abutment (or fixture) replicas.

Add a block of resin to each square impression coping.
Do not connect the adjacent resin blocks yet. Allow the resin to sit.

Now add resin to connect the resin block and hence the
impression copings to each other. Allow resin to set. This is now a
“confirmation jig.” (Figure 27).

Take this assembly to the patient’s mouth and try
it in. If it seats and does not rock, the accuracy of the master cast is
confirmed. If not, a new impression could be made.

Figure 27: Confirmation Jig

8.4. Wax-Up of Implant Framework

Armamentarium

Waxing instrument kit and #7 wax spatula

Paper towels and piece of nylon cloth

Bunsen burner

Casting wax

Gold cylinders and plastic burn-out sleeves

Proxabrush

Thin separating disk and mandrel

Slow speed straight handpiece and acrylic burs

Acrylic resin power liquid and powder, two Dappen dishes
and two small disposable brushes

Adjust the top of the waxing sleeves (and, if applicable,
guide pins) to within ~0.5 mm of the opposing occlusion.

Attach the gold cylinders or waxing sleeves together with
a small amount of resin.

Flow wax onto the entire gold cylinder or plastic waxing
sleeve but not into the gold cylinder or implant replica.
(Figure 29).

Figure 29: Wax-up around the gold
cylinders

Wax-up buccal, occlusal and lingual to complete anatomic
contour. (It may be necessary to form a type of modified ridge-lap contour to
achieve the desired esthetic result. This often occurs when the implant is
necessarily placed lingually and a root form must be developed facially to hide
the implant.)

Ensure that the correct interproximal embrasures have been
created by placing the proxy brush from all angles - buccal and lingual.

Have the full contour checked by an instructor.

Modification for RPD:

After full contour wax-up, but before cutback for
porcelain, place cast with wax-up on surveyor table.

Adjust table so that the guiding surfaces and
undercuts of other abutment teeth are properly evaluated, i.e., that
0.01” undercut exists on other abutments in the same places as were
determined on the study cast.

Place wax knife in surveyor arm and trim guide planes.

Place cingulum rest seat with edge of blade and build
up lingual edge of rest seat with #2 waxing kit instrument.

Modify bracing area to be parallel with guide plane.
Lower facial height of contour, if necessary, with the same wax knife.

Place rest seat using #6 round bur in the hand to its
full depth at the marginal ridge and full depth at the triangular fossa.

Round sharp edges of all rest seats with the #7 wax
spatula.

Proceed with cut back as in #9 below.

Cutback for porcelain.

Using the sharp end of a cleoid-discoid, make 1.5 mm
depth cuts in areas where porcelain is to be applied. Final coping thickness in
wax: no less than 0.4 mm facially and 0.6 mm occlusally.

Reduce wax between depth cuts with #7 wax spatula.
(It may be necessary to reduce acrylic with a slow-speed acrylic bur.)

All joints (between pontics and abutments and between
pontics and pontics) should be a minimum of 3.0 mm long and 2.0 mm wide.
Ideally a joint should be 4.0 mm long and 3.0 mm wide. A metal occlusal contact
in the marginal ridge areas may be necessary to achieve this goal.

Contact areas should be ½ in the metal buccolingually
and inciso-gingivally. Anteriorly the interproximal strut can be cut back
facially about 0.5 mm and covered with porcelain for esthetic reasons.

The collar on the proximal or lingual should form a
buttressing shoulder for the porcelain. The shoulder should be rounded
internally but at right angles externally. No internal angle should be sharp.
The shoulder should be smoothly continuous with the interproximal struts.

The pontic lingual buttress should be at least 3.0 mm
in width occluso-gingivally for heat radiation purposes. This metal may
continue on to the tissue surface in short pontic spaces.

Section the wax-up at the level of the solder joint
with the thin separating disc.

Check to assure screws are tightened and then flow wax
between cut pattern to rejoin.

Check again with proxabrush in embrasure areas to
assure sufficient space for cleaning.

Smooth wax with a folded paper towel and/or nylon
cloth.

Sprue and invest wax-up.

Goals of Your Wax-Up

When you have finished your wax patterns, ask yourself
the following questions:

Is the prosthesis waxed to the full contour?

Has a proper occlusion been developed?

Are there centric stops (check with talcum powder on
occlusal surface)?

Are there sharp internal details? Are there voids
anywhere?

Has interproximal contact been restored? (Should not be
point contact, but an area of contact.)

Does the crown maintain continuity with the adjacent teeth
in the arch?

Do the cusp tips line up?

Is the buccal surface curvilinear?

Are the coronal heights of contour for the buccal and
lingual surfaces located in the proper position?

Is the occlusal anatomy properly carved?

Is the finish line on the coping properly finished?

Is there enough space for porcelain application?

Are the joints long enough and the embrasures big enough?

8.5. Metal Framework Try-In

This step is the same as the framework try-in method
for FPD’s. However, dental implants differ from teeth both
physiologically and histologically. While natural teeth are anchored by
surrounding periodontal ligament, dental implants are anchored into alveolar
bone similar to that of ankylosed teeth. So dental implants do not have any
capability to adapt itself to the non-passive fit framework, unlike natural
teeth. The lack of periodontal ligaments induces more trauma. In cases with
implants a passive fit of the metal framework is desired. The framework for
dental implants has to be completely passive to avoid any
fixture trauma, gold screw loosening or fracture.

Takes healing abutments and places in appropriate cleaning solution
(should be done at same time as above).

Cleans inside of implant with water
spray.

Suctions.

Inserts proper abutment when
applicable.

Attaches prosthesis with one screw. If more
than one implant abutment, the single screw will seat one of the castings
completely. If a gap appears between the bottom of the casting that is not
screwed in, then remove the first screw, remove the casting, and proceed with
#6 below.

Extraorally sections casting slowly and
carefully through the thickest casting joint (usually between the pontic and
largest retainer casting). It may be necessary to cool the casting by dipping
it in a cup of water at times. It is also advisable to section casting from all
sides so that thin disks are less likely to bend and break. When 7/8 of the
joint has been cut through, an attempt should be made to bend and break the
remainder of the casting by hand.

Places thin separating
disk and mandrel in straight handpiece and hands to dentist.

Using the same disk, smooth the cut surface
of both pieces. If the pieces are not smoothed, the rough surfaces could bind
on each other during seating of the sections. Do not reduce casting
surfaces any further.

Hands dentist a 2 x 2”
sponge.

Places 2 x 2” sponge as a drape
in back of mouth.

Places Acrylic resin powder and
liquid in separate Dappen dishes

Places both castings with screws being
careful to line up buccal and lingual surfaces.

Casting does not seat on abutment. Check
tightness of contact areas with floss.

Hands
dentist cotton rolls.

If no rocking is present or is corrected by
slight adjust-ment to bottom of casting, places cotton rolls for mois-ture
control around casting and dries casting (especially between the cut surfaces)
with a gentle air blast.

Places a drop of Acrylic resin monomer in
joint space, using #0 brush.

Holds two dappen dishes, one
with Acrylic resin powder monomer and one with powder.

Paint Acrylic resin powder in and adjacent to
joint spaces with “liquid and powder” method.

Mixes fast-setting plaster to thick cream consistency with cement
spatula and places about a 3x2x6.0 mm line of mixed plaster on the end of a
tongue blade

Quickly places tongue blade/plaster gently on
occlusal surfaces of castings. Only the occlusal 1/4 to 1/3 of castings should
be in the plaster

After the plaster has set, removes gently
from mouth and inspects. If any plaster has flowed under margin of the casting,
the exercise must be repeated.

Recements interim restoration.

Proceeds to laboratory for investing and
soldering.

Porcelain Application

Porcelain is applied in the laboratory – See
Crown and FPD Manual. Guide pins are kept in to assure maintenance of screw
access opening. If cemented: cement with temporary cement

8.6. Initial Delivery

Check the fit, proximal contact and occlusion. Final
restoration is tightened using gold screws according to the
manufacturer’s recommendation or is temporarily cemented. (Figure
31 & 32).

Insertion

Armamentarium (Figure
31)

Figure 31: Armamentariumie Torque Driver
Kit

Driver kit (dispensary)

Gold screws (one per fixture) or cement

Basic setup

Cotton pellets

Cavit

Technique

If screw retained:

Seat FPD with a single gold screw on the most medial
fixture.

Tighten screw to light pressure.

Confirm that FPD has no lateral movement.

Seat screws on most distal abutments.

Seat screws on intermediate abutments.

Tighten screws in above sequence and confirm occlusion.

Place cotton pellet over screw and seal with cavit.
(Figure 32)

If cemented:

Cement with temporary cement.

Table 3: Overview (summary) of FPD
from Impression to Delivery:

The impression is made utilizing square impression
copings with an open top tray, or tapered impression copings and a closed top
tray. Occlusal records are made in the normal fashion. A regular record base
could be used or a record base can be constructed incorporating gold cylinders,
which can be screwed in the mouth. This “cylinder record base”
provides retention and will improve accuracy of the record.

The impression is poured with the inclusion of
abutment/fixture replicas, which simulate the implant abutment/fixture.

A gold cylinder is screwed to the top of the abutment
replica on the model. It is held in place with a laboratory screw or guide pin,
which will extend above the occlusal surface. The purpose of the laboratory
guide pin is to maintain (during all laboratory procedures) an opening in the
occlusal table of the fixed partial denture for the placement of a gold
prosthetic screw to fasten the prosthesis to the abutment. This laboratory
guide pin will be replaced with a gold screw at the time of intraoral
insertion.

The gold cylinder will be incorporated into a wax-up
(cast together) for the framework of the fixed partial denture. The design of
the wax-up will follow conventional metal ceramic principles. The cylinder
provides a machined fit to the abutment.

The fit of the frame at metal try-in is tested by
observing lateral movement. If the fit is correct, there will be no perceptible
movement, and clinically the margin of the cylinder and the abutment will line
up with no apparent opening.

After confirmation of the framework, the porcelain is
applied in the conventional manner. Care is taken to maintain the opening
around the laboratory guide pin.

At the bisque try-in, the shape and shade is evaluated
and the occlusion is confirmed. The fixed partial denture is glazed and
finished in the conventional manner. Care is taken in all steps to avoid
altering the gold cylinder (use protection caps).

The fixed partial denture is inserted by tightening the
gold screw. After securing the screw, a cotton pellet is placed over the screw
head and a temporary stopping material, such as cavit, is used to seal the
opening.

After an adequate trial period, the cotton pellet and
cavit is removed. Gutta-percha is placed over the gold screw, and a tooth
colored resin is used to fill the opening.

8.7. Check Up and Post Insertion Care

1st Recall

Recall in two weeks and remove FPD.

Evaluate and adjust for cleansability, tissue health, and
occlusion, if necessary.

Reseat and secure in previous sequence.

If acceptable to operator and patient, place gutta percha
over screws and seal with composite resin.

Figure 32: Initial Insertion: Cotton &
Cavit

2nd Recall

At 3, 4 or 6 month recall, perform periodic examination of
entire mouth. Update radiographs as needed. Be sure to only use plastic scalers
around implants. Radiographs of implants should be made once per year. Implant
prostheses are not routinely removed unless there is a problem, such as pain or
a need for repair or remake of the prosthesis.

9. References

Binon PP. Evaluation of The Effectiveness of A Technique to
Prevent Screw Loosening. Journal of Prosthetic Dentistry. 79(4):430-2, April
1998.